I currently have a 5.5gal tank and heater, but nothing else with it.
Do I need to cycle a 5.5 gal if I do frequent water changes with dechlorinator?
Also, do I need a filter?

My current betta is at the end of his days, so I'm sure it's just a matter of time before I could move a new male into the 10 gal my current one is in. (It's a community though, I'd have to see his demeanor).

+1 to shellieca.
Filters and cycling usually make maintenance a little easier in tanks 5 gallons and above, which is why most choose to do so, but its certainly all up to you whether you want to go down that road or not. You can definitely go without a filter if you keep up with the water changes, 1 50% and 1 100% per week with gravel vacuuming should do the trick. ;)